Sighting apparatus.



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W. A. BURNS.

SIGHTING APPARATUS.

APgLlcATIoN man luLY 31. 1916.

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W. A. BURNS.

SIGHTING APPARATUS.

APPLICATION FILED JULY 31. |916.

Patented J an. 9, 1917.

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ITED STATES PATENT oEEcE.

WILLIAM ALBERT BURNS, OF DRUMMONDHILL, SCOTLAND, ASSIGNOR T0 VICKERS LIMITED, OF LONDON, ENGLAND.

SIGHTING APPARATUS.

To all whom t may concern Be it known that I, l/VILLIAM ALBERT BURNS, a subject of the King of Great Britain, residing at Drummondhill, in the county of Inverness, Scotland, have invented certain new and useful Improvements in Sighting Apparatus, of which the following is a specification.

This invention relates to sighting bars or sighting telescopes embodying devices to enable the line of sight to be corrected to compensate for deviation of the projectile due to movement of the gun platform at the moment of firing. This deviation is often known 'as the speed error and requires speed allowance or speed correction to compensate for it.

Means have already been used or proposed for putting the necessary speed allowance on a sight bar, such means comprising a rotary cam or a rotary crank actuated by gearing carried by the gun mounting, or an adjustable member pivotally connected to the sighting apparatus, this member being set to the speed and direction of movement of the platform carrying the gun so that during the elevation and traversing of the gun a correction for the speed and direction of movement of the platform is automatically given to the sighting apparatus. These devices may be divided into two classes. The first class comprises devices for correcting` for speed error in the vertical plane only in cases where the gun has a large vertical arc of fire (that is to say can be directed at targets much above or below the guns own level) but a very small amount of lateral traverse. The second class of device is intended to put speed correction on the sights or sight bar in both the horizontal and vertical planes, in cases where the gun can be traversed laterally over a considerable horizontal arc in addition to having a large vertical arc of fire; a gun having a considerable horizontal arc but a small vertical one may be considered as a particular case of this latter class.

According` to the present invention the raising or lowering of one end of the sight bar to correct for gun platform speed is eected automatically, as the gun is laid by mechanism of such a character that the ratio between the respective distances measured horizontally from two points on Specification of Letters Patent.

Patented Jan. 9, 1917.

Divided and this application filed July 31,

the sight bar to a. vertical plane perpendicular to the line between them is equal to the ratio of muzzle velocity of the projectile to the gun-platform speed, this vertical plane passing through the axis of the gun trunnions. Various constructional arrangements are hereinafter described for the purpose in view some being adapted to correct for speed with changes of elevation or depression of the gun only while others are adapted to make the necessary speed correction required not only with changes of elevation or depression but also of lateral traverse. In several constructional arrangements hereinafter described the point of intersection of the trunnions axis and the vertical axis of the cross head of the gun mounting lies in the metal of the gun. In the case of light ordnance, however, the aforesaid point of intersection may lie outside the metal of the gun; the gun may for example be raised above its trunnions axis by being provided with a downwardly extending bracket or pair of lugs in which case the sight bar may lie vertically below the gun and pass through the aforesaid point of intersection, thereby eliminating link or other mechanism for controlling the sightbar or other sighting member, as hereinafter explained.

In the accompanying drawings, Figure l is a side elevation, and Fig. 2 is an end view, of a Maxim machine gun fitted with a form of device for mechanically adjusting a sight bar for speed in th-e vertical plane. Figs. 3 to 6 are diagrammatic views of one form of device for adjusting a sight bar to compensate for speed error7 in both the vertical and horizontal planes; and Figs. 7 to 12 are similar views of means for eifecting the same dual compensation by means of an alternative form of mechanism. Figs. 13 and 14n illustrate a typical machine gun in which the gun itself is supported above its trunnions axis, as hereinafter explained.

In Figs. l and 2 the front portion of the sight bar S is carried by a pivot. or swivel P at the fore end of the gun casing G, the rear portion of the bar being carried by a bridge or arch A pivoted close to but in rear of the trunnion axis. The pivot blocks K', K2 may be carried by suitable extensions or guides C, C2 formed on the crosshead C and means may be provided so that the iirer alter the speed distance SP of these pivot blocks behind the trunnion axis to suit the speed of the gun platform. Instead of the point P being at the front end of the gun, that is to say in advance of the trunnions, it may be to the rear of the latter, but in this case the pivot blocks K', K2, are carried in advance of the trunnion axis and not as shown in Fig. l.

Referring now to cases in which compensation is required in two planes, Fig. 3 is a side elevation, accompanied by two end views, of a typical gun carrying a sight bar S above it, the front end P', or front pivoting point of the bar, being so mounted on a link L that the bar S is parallel to the gun axis when the gun is horizontal as in the figure. The rear end or rear pivoting point P may be carried by a bracket B rigidly attached to the base of the cone E, or to some otherpart of the gun mounting or its surroundings, which takes no part in the movement of the gun either in elevation or training, that is to say the rear pivoting point is immovable except for speed setting, to alter the value of SP. The rear pivot point P lies behind a plane containing the axes both of the trunnions and of the vertical pivoting rod H at a distance SP equal to the speed7 in terms as before of the guns velocity the front pivoting point being at the distance VEL in front of the aforesaid plane. Means may be provided to alter the distance SP as required, but otherwise the points and distances are fixed.

Fig. 4 shows how, when the gun is depressed, a depression angle Z is put on the normal line of sight, and when the gun is elevated a similar elevation angle e is put on.

Fig. 5 shows the gun in plan, assumed to be pointing dead ahead, that is to say in the direction of movement of the platform, the line of sight being then parallel to the axis of the gun.

Fig. 6 shows how when the gun is traversed to the right or left of the ahead line a, L, right or left deflection respectively is put on the line of sight. It can be deduced from well known mechanical and geometrical considerations that these elevation depression or deflection angles are exactly those required to compensate in each case for the s eed errors.

IInstead of mounting the sight above the gun, analogous means may be employed to carry the bar at the side of the gun, and in such cases the arrangement illustrated in Figs. 7 to l2 may be employed. Fig. 7 is a side elevation showing the general arrangement. Fig. 8 an end elevation, and Fig. 10 is a plan, all with the gun horizontal. The front end of the sight bar S is carried by a pivot point P at the end of a rigid bracket K (Fig. l0) formed on the front end of the gun or gun casing. The

rear end of the sight or rear pivoting point P is at the upper end of a bracket B carried by a link or horizontal arm N, itself pivotally attached to a carrier arm M formed on the gun carriage or crosshead C. The free end of the link arm N is attached by a connecting rod or cross-link T to an immovable point or bracket E, which in the example shown is formed on the cone or base E the whole arrangement constituting a parallel-motion system whereby the axis n, n (Fig. 1l) of the link arm N may be kept parallel to the dead ahead line a, h, of the platform at all angles of traverse of the gun. `When the gun is horizontal and pointing dead-ahead (as in Figs. 7 and l0) the points P and P lie in the horizontal plane of the axis of the bore (assuming the axis to cut that of the trunnions as shown in the figures) and the point P is at a distance VEL as before in front of the trunnion axis, and the point P at a distance SP in rear of this axis. Fig. 9 shows how depressing the gun puts depression on the line of sight, and Fig. 11 shows how left traverse of the gun puts on left deflection. In some cases, where great rigidity is required there may be substituted for the link N and bracket M, an arc 7 (Fig. 12) and a sliding piece U carrying the rear pivoting point P.

In the above figures and in the construction illustrated in Figs. 3 to 6 a sight bar has been shown mainly in front of the trunnions, but sighting gear may be made on the same principles having a bar mainly in rear of the trunnions. Inthis case the point P is in advance of the trunnion axis in either construction, the point P being toward the rear. Obviously this will entail the reversal of some of the conditions in the latter construction.

In the constructional arrangements illustrated in Figs. 3 to l2, the point of intersection of the axis of the gun trunnions and the vertical axis of the cross-head lies in the metal of theJ gun. In the case of light ordnance, however, the said point of intersection may lie outside the gun and a construction of this kind is shown in Figs. 13 and 14. The gun G is supported upon two lugs G2 G2 pivotally attached to the upstanding arms C3 C3 of the crosshead C. The main pivot P of the sight bar S is carried on an extension H of the non-revoluble central rod H, and the rear pivot P is on a bracket G3 depending from the gun, these points being such that the axis of the sight bar is parallel to the axis of the gun and passes through the intersection of the trunnions axis and the vertical axis of the rod H, when the gun is in the horizontal position. The extension H extends forwardly with respect to the vertical plane containing the trunnions axis, the point P being in advance of this plane at a distance SP, while the point P is situated to the rear of the same plane at a distance VEL, as explained in the earlier part of this specification. The front and rear ends of the sight bar are provided with any known form of sighting members, as shown in Fig. 13. It will be understood that as the gun is elevated or depressed -the correct angle between the gun axis and the line of sight is automatically maintained. It is however to be observed that the correct line of sight is established without resorting to link mechanisms for carrying the sight bar. It is also to be noted that the deflection correction required as the gun is traversed laterally is made automatically by reason of the angular movement of the gun relatively to the stationary condition of the extension H carrying the front pivot P of the sight bar. It will be obvious that in this construction, as already pointed out in connection with certain of the constructions above described, the points P and P may be interchanged as regards their position relatively to the trunnions axis.

While this invention has been described as applied to the sights of guns carried on aircraft, it is applicable generally to the sighting of guns carried on any nature of moving platform.

What I claim and desire to secure by Letters Patent of the United States is 1. Sighting apparatus having a pivoted sight bar in combination with means for automatically rocking the sight bar as the gun is being laid, said means being such that the ratio between the respective distances, measured horizontally, from two points on the sight bar to a vertical plane perpendicular to the line between them and passing through the axis of the gun trunnions, is equal to the ratio of muzzle velocity of the projectile to the gun-platform speed.

2. Sighting apparatus having a pivoted sight bar in combination with link mechanism for automatically rocking the sight bar as the gun is being laid, said link mechanism being so proportioned that the ratio between the respective distances, measured horizontally, from the points of support of the link mechanism on apart that moves in elevation with the gun and on a part that does not move with the gun in elevation, to a vertical plane passing through the axis of the gun trunnions, is equal to the ratio of muzzle velocity of the projectile to the gun-platform speed.

8. Sighting apparatus having a pivoted sight bar in combination with link mechanism, of which the sight bar forms part, for automatically rocking the sight bar as the gun is being laid, said link mechanism being so proportioned that the lratio between the respective distances, measured horizontally, from the points of support of the link mechanism on a part moving with the gun in elevation and on a part that does not move with the gun in elevation, to a vertical plane passing through the axis of the gun trunnions, is equal to the ratio of muzzle velocity of the gun, to the gun-platform speed.

4. Sighting apparatus having a sight bar in combination with means for pivotally connecting it at one side of the gun trunnion axis to a part moving in elevation with the gun and means for pivotally connecting said sight bar to the gun mounting at the other side of the gun trunnion axis the pivotal points of connection being so arranged that the ratio between the respective distances, measured horizontally, from said pivotal points to a` vertical plane passing through the trunnion axis is equal to the ratio of muzzle velocity of the projectile to the gun-platform speed.

5. Sighting apparatus having a sight bar in combination with means for pivotally connecting it at one side of the gun trunnion axis to a part moving in elevation with the gun, means for pivotally connecting said sight bar to the gun mounting at the other side of the gun trunnion axis, the pivotal points of connection being so arranged that the ratio between the respective distances, measured horizontally, from said pivotal points to a vertical plane passing through 9 the trunnion axis, is equal to the ratio of muzzle velocity of the projectile to the gunplatform speed, and means for adjusting the distance between the trunnion axis and the pivotal point of connection of the sight bar with the gun mounting, tg agree with difer- 6. Sighting apparatus having a sight bar in combination with means for pivotally connecting its front portion at a point in front of the gun trunnions to a part moving in elevation with the gun and means for pivotally connecting its rear portion to the gun mounting at a point to the rear of the gun trunnions, the ratio of the distances, measured horizontally, of the said points from a vertical plane containing the axis of the trunnions, being equal to the ratio of muzzle velocity of the projectile to the gunplatform speed.

7. Sighting apparatus having a sight bar in combination with means for pivotally connecting its front portion at a point in front of the gun trunnions to a part moving in elevation with the gun and means for pivotally connecting its rear portion, at a point to the rear of the gun trunnions, to a part of the mounting moving in training only, the ratio of the distances, measured horizontally, of the said points from a vertical plane containing the axis of the trunnions, being equal to the ratio of muzzle velocity of the projectile to the gun-platform speed.

8. Sighting apparatus having a sight bar in combination with means for pivotally connecting its front portion at a point in front of the gun trunnions t0 a part moving in elevation With the gun and means for pivotally connecting its rear portion to a fixed part 0i the gun mounting` at a point to the rear of the gun trunnions, the ratio of the distances, measured horizontally, of the said points from a vertical plane Containing' the axis of the trunnions, being` equal to the ratio of muzzle velocity of the projectile to the gun-platform speed.

9. Sighting apparatus having a sight har in combination with means for pivotally connectingl it at one side of the gun trunnion axis to a part moving with the gun and means for pivotally connecting the sight bar to a fixed part of the mounting at the other side of the trunnion axis so that as the gun is traversed the line of sight is automatically deflected to allow for gun-platform speed.

10. Sighting apparatus having a sight bar in combination with means for pivotally connecting it at one side of the gun trunnion axis, to a part moving With the gun and parallel link mechanism by which the sight bar is connected at the other side of the trunnion axis to a fixed part of the mounting.

In testimony whereof, I hereto affix my signature.

WILLIAM ALBERT BURNS.

Copies of this patent may be obtained for ve cents each, by addressing the Commis oner of Patents. Washington, D. C. 

